I think if they really delay it, they should announce it official and dont make a twitter post and delete the post after some minutes. But i dont think this will come out this year, they have announced gameplay 2 times and we have still only cinematic trailers. So i dont think what i should think about a 2017 or 2018 announcement.
I think the sinking city (another Call of Cthulhu game) will come out earlier, it is announced for 2018 and from the sinking city we already have gameplay...
What is with the for the e3 announced gameplay walktrought with developer commentary?
"We’ll be showing Call of Cthulhu at the #E32017 Focus Home Interactive booth on June 13-15 with a gameplay walkthrough and developer commentary."